1. Field of the Invention
This invention is a technical innovation that relates to simplification and improvement of alignment accuracy of an alignment (optical axis alignment) structure of an image pickup optical system in a lens barrel.
2. Description of Related Art
Conventionally, a lens barrel that is applied to an image pickup apparatus such as a camera is constituted by an image pickup optical system including a plurality of optical lenses, a plurality of cylindrical or annular barrel members and a drive mechanism and the like Among these, the plurality of barrel members include, for example, lens holding barrels that are configured to hold a plurality of lens groups constituting the image pickup optical system, respectively, and to enable advancing/retreating movement in a direction along the optical axis for focusing or zooming.
For a conventional lens barrel, to maintain the optical performance of the image pickup optical system, assembly is performed after adjusting the eccentricity of the optical axis center of the plurality of lens groups and performing alignment (optical axis alignment) in order to substantially match the optical axes of the respective lens groups. Consequently, as disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2008-216906 and Japanese Patent Application Laid-Open Publication No. 2008-170889, various structures have been proposed for performing alignment of a plurality of lenses constituting an image pickup optical system in a conventional lens barrel.
In a lens barrel disclosed in the aforementioned Japanese Patent Application Laid-Open Publication No. 2008-216906, alignment of lenses is performed by pressure welding and fixing a plurality of lens holding barrels using countersunk head screws.
A lens barrel disclosed in the aforementioned Japanese Patent Application Laid-Open Publication No. 2008-170889 includes: a lens frame; a holding barrel including a flange piece having opposing faces orthogonal to each other and protruding in an optical axis direction in a manner that opposes an outer circumferential face of the lens frame; a holding plate held between the outer circumferential face of the lens frame and the flange piece of the holding barrel; an adjustment plate provided on the holding plate; and a plate spring that is provided at a position facing the holding plate with the optical axis interposed between the plate spring and the holding plate, and that urges the lens frame in the holding plate direction from the outer circumferential face side; in which the lens barrel is configured so that eccentricity adjustment can be performed in a direction orthogonal to the optical axis by exchanging adjustment plates that have different thicknesses. In this case, a configuration is adopted that urges the lens frame by means of an urging member (a plate spring or a countersunk head screw or the like) to thereby press the adjustment plate.